Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F13: Biomaterials IIFocus Live
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Sponsoring Units: DBIO Chair: Pupa Gilbert, University of Wisconsin - Madison |
Tuesday, March 16, 2021 11:30AM - 12:06PM Live |
F13.00001: Patterns in skeletal biomineralization Invited Speaker: Susannah Porter Mineralized skeletons evolved many times in the eukaryotes, including dozens of times in animals. These numerous independent acquisitions provide an opportunity to test hypotheses about the origin and evolution of skeletons, including factors controlling the choice of mineralogy and the reasons why mineralized skeletons evolved. Earlier work showed that the choice of carbonate mineralogy (aragonite vs. calcite) in animals reflects the chemistry of seawater at the time the skeleton evolved. We have since expanded this dataset to include other mineralogies and other eukaryotes and have identified >80 acquisitions of mineralized skeletons. Several patterns have emerged. First, acquisitions among animals are clustered, with more than half appearing in the early Cambrian, and another 25% in the Ordovician through Devonian. A smaller cluster of acquisitions occurred in the mid-Triassic to Jurassic, with nearly all in the cnidarians and annelids. In contrast, skeletal acquisitions in non-animal eukaryotes are distributed throughout the Phanerozoic, with no obvious clustering in time. This supports the view that ecological factors affecting only animals (e.g., the appearance of carnivores), rather than physical factors affecting all marine organisms (e.g., increased seawater [Ca2+]), drove biomineralization in animals. Second, acquisitions of phosphatic skeletons are concentrated in the Neoproterozoic and Cambrian, perhaps reflecting higher seawater phosphate at this time. Finally, the distribution of mineralogies tends to be non-uniform: 73% of the acquisitions in the animals and all of the acquisitions in seaweeds were carbonate, whereas all of the acquisitions in the stramenopiles were silica. Whether this reflects functional constraints, e.g. related to unicellular vs. multicellular organization, or phylogenetic constraints, e.g. reflecting underlying homology of genes involved in the nucleation and/or inhibition of these particular minerals, is not clear. |
Tuesday, March 16, 2021 12:06PM - 12:42PM Live |
F13.00002: Applications of molecular taphonomy to the invertebrate fossil record Invited Speaker: Corinne Myers In the last several years studies have demonstrated the utility of PhotoEmission Electron spectroMicroscopy (PEEM) to observe exceptional preservation of organic matrix components and shell microstructure in fossil mollusks. Comparisons to modern representatives suggests very strong similarity and potential links to paleoenvironmental conditions (e.g., temperature). Current work must focus on replicating these results across additional time periods, types of biomineralizing species, and taphonomic histories. Future work on the utility of hyperspectral imaging, the geography of preservation, influence of large-scale ocean-climate regimes (e.g., icehouse vs. greenhouse; calcite vs. aragonite seas) and complementary analyses (e.g., Raman spectroscopy), will provide additional clues into the molecular and structural preservation of biominerals, as well as their evolution through geologic time. |
Tuesday, March 16, 2021 12:42PM - 12:54PM Live |
F13.00003: Probabilistic Modeling of Hyaluronan Synthesis and Secretion Jan Scrimgeour The synthesis of hyaluronan (HA) from the surface of living cells is essential to the maintenance of tissues in living systems. HA synthesis is controlled by the hyaluronan synthase enzyme, which assembles the polymer chain, and extrudes it through the cell membrane before it is released into the extracellular space. This process forms a critical link between the state of the cellular system (protein expression, metabolism, etc) and the properties of cellular interfaces, the extracellular matrix and many biofluids. I present a probabilistic model that allows an examination of secretion of HA by the synthase enzyme. This model provides two key insights. First, it provides a foundation for the prediction of HA molecular weight distributions that are tethered to, and released from, cell surfaces. This provides critical insight into both naturally occurring molecular weight distributions and those produced by in vitro synthesis. Second, it suggests that time-resolved analysis of the HA molecular weight distributions produced by living cells can reveal critical details of hyaluronan synthase function. In the future, such models may assist in the prediction of the physical properties of HA-rich materials and their response to changes in cell state. |
Tuesday, March 16, 2021 12:54PM - 1:06PM Live |
F13.00004: First structural study of gel inside the electro sensory organs of cartilaginous fishes Alauna Wheeler, Molly Phillips, Manping Jia, Marco Rolandi, Chris Amemiya, Linda S. Hirst Cartilaginous fishes detect electric fields in their environment using the sensory organs called Ampullae of Lorenzini (AoL). Although the organs were discovered hundreds of years ago, little is known about the gel inside the AoL. Some components of the gel have been identified recently, including chitin and other polysaccharides, but the structure of the gel is yet unknown. Using data collected from atomic force microscopy (AFM), proton conductivity, and x-ray scattering experiments, we present the first microscopic descriptions of the AoL gel structure. We include an investigation of the structural influence of the protein components in the gel by comparing the data of the gel with data from aliquots digested with proteolytic enzymes. We find evidence that the AoL gel is colloidal in nature, stabilized by a protein network. |
Tuesday, March 16, 2021 1:06PM - 1:18PM Live |
F13.00005: Resonance Raman measurements on fossilized remains show ancient heme-globin complex Brandon Long, wenxia zheng, Mary Schweitzer, Hans David Hallen Still-soft, hollow, and flexible structures morphologically consistent with blood vessels recovered from demineralized dinosaur bone were studied with resonance Raman techniques to test the hypothesis that these vessel-like structures are original to the dinosaur, and that they maintain endogenous molecular characteristics. Modern, artificially aged analogs show the beginnings of similar processes. We probed these samples using resonance Raman at two different wavelengths. Doubly selective resonant Raman techniques confirms the co-location of a heme moiety onto a larger globin protein by probing both heme vibrational modes and a excitation-resonant bond simultaneously. The existence of a stronger resonance Raman signal level in the green compared to blue excitation is consistent with a hemoglobin, not just heme, absorption resonance. These data imply that heme moieties in the soft structures are attached to remnant globins, or fragments thereof. Further, analysis of the Raman spectra of these hemoglobin remnants show damage to the outer regions of the heme ring, indicative of diagenetic change consistent with an ancient endogenous source. Separately, the formation of goethite crystallites still attached to the hemoglobin remnant suggest a possible mechanism for preservation. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Live |
F13.00006: Ptychography of diatoms reveals chemically inhomogeneous biosilica cell walls Jiaqi Li, Pupa Gilbert Diatoms are a large group of unicellular eukaryotic microalgae, renowned for their beautifully intricate biosilica cell walls (BCWs) and their abundance in sea and fresh water. BCWs exhibit the highest specific strength in all known biological materials and may serve as a powerful armor against parasites and grazers for the ecological success of diatoms. Diatom BCWs exhibit characteristic nanopatterns indicating that silica formation is genetically controlled by silica-forming proteins, presumably functional during silica deposition. Understanding the biomineralization of BCWs is of great interest in biological and ecological studies. Here, we studied the biosilica coordination and the morphology of diatom BCWs using the synchrotron-based x-ray spectromicroscopy (ptychography), with a 10nm spatial resolution. Our preliminary data showed that the BCWs of wild type Thalassiosira pseudonana have three different coordination environments. The girdle band of T. pseudonana has two layers of silica. The outer layer biosilica is less polymerized than the inner layer as the Si K-edge of the outer layer is 0.3 eV lower. The Si environments of valves are heterogeneous with varying degrees of silica polymerization and degrees of long-range ordering. |
Tuesday, March 16, 2021 1:30PM - 1:42PM Not Participating |
F13.00007: Inhomogeneous degree of connectivity preference and computational efficiency in the olfactory system of the fruit fly Lishan Cheng, Ching-Che Charng, Kuan-Lin Feng, Li-An Chu, Chung-Chan Lo, Ann-Shyn Chiang, Ting-Kuo Lee The mushroom body (MB) is one of the olfactory information processing centers of fruitflies. Receiving information at calyx, different subtypes of Kenyon cells (KC), the intrinsic neurons of MB, respectively translate odorant stimuli into learning or memory behaviors. There were conflicting results reported about the network structure being random or with stereotypical preference. Based on the FlyEM dataset, we quantitatively measured the degree of randomness of each KC subtype by utilizing several exploratory data analyses. The results reveal that the learning-related network is strongly random, while the memory-related circuitry only possesses a mild degree of randomness. In addition, the connectivity preference of calyx corresponds with several innate features, including the development order of KC and the neuronal spatial arrangement of upstream brain regions. While the small-world network coupling, an almost regular network structure but with a few disordered connections, is known to possess high signal-propagation speed, MB displays the opposite topological characteristic: a highly random network but with slight connectivity preference. How a moderate degree of structural preference affects odorant discrimination and computational efficiency would be further discussed. |
Tuesday, March 16, 2021 1:42PM - 1:54PM Live |
F13.00008: Remote Data Processing Using Crowd-Sourced Cloud-Computing Benjamin Fordyce, Pupa Gilbert Pandemic circumstances require creative solutions to research problems. Here we discuss processing spectromicroscopy data acquired with synchrotron spectro-microscopy on freshly formed coral skeletons. This model, however, can be used for processing any data that require decision-making and are therefore viable to human error. |
Tuesday, March 16, 2021 1:54PM - 2:06PM Live |
F13.00009: Inelastic neutron scattering of perdeuterated cellulose Howard Wang, Yoshiharu Nishiyama, Xin Zhang, Robert M Briber, robert russell, Siqian Chen, Yanjun zhang Perdeuterated cellulose has been prepared by feeding acetobacters with deuterated glycerol, and measured inelastic neutron scattering with planar orientation to obtain the elastic tensor. Perdeuteration allows for the measurement of anisotropic inelastic scattering spectra with low background compared to the hydrogenated one, which has high incoherent scattering depriving of structural information. Acoustic branch is observed around elastic line of 2 0 0 reflection, perpendicular to the pyranose ring, whereas not along the chain direction. The data are analyzed and discussed in the context of intrinsic structure factors of natural cellulosic material as well as the constraints in specimen preparation and measurement techniques. |
Tuesday, March 16, 2021 2:06PM - 2:18PM Live |
F13.00010: Nanoscale crystal orientations in tooth enamel in monsters of the past and their modern counterparts Cayla Stifler, Rajesh V Chopdekar, Pupa Gilbert Teeth and especially the outer enamel(oid) layer are adapted to the particular feeding habits and wear of the animals forming them. Where tooth shape is ambiguous, enamel microstructure is used to infer whether or not a fossilized tooth belonged to a predator. However, most of the existing literature focuses on the physical elongation of enamel nanocrystals, and not on their crystalline orientations, which have been shown to a) not always correlate with the elongation direction of the nanocrystals (https://doi.org/10.1038/s41467-019-12185-7) and b) correlate with enhanced hardness and stiffness (https://doi.org/10.1016/j.actbio.2020.07.037). We used PIC (polarization-dependent imaging contrast) mapping at the calcium L-edge (https://doi.org/10.1021/jacs.8b05547) to reveal the crystal orientations of enamel(oid) crystals in monsters of the past, including T. rex, megalodon and ancient and modern sharks and bears. Comparison of PIC from these different top predators indicates that the crystal orientation patterns are well preserved over evolutionary time, and that they correlate with function. |
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